Studies have shown that the consumption of raw garlic provides numerous health benefits as an antihyperlipidemic, antimicrobial, antiplatelet, antioxidant, anti-diabetic, and as a vasoprotective agent.
Allicin is widely believed to be the pharmacologically active component responsible for many of these beneficial health effects of garlic consumption. Allicin is produced by an enzymatic reaction of allinase and alliin. The allinase enzyme is stored in a separate area from the alliin within the garlic and combines with alliin in raw garlic when the garlic is crushed or macerated to produce allicin. Because allicin is unstable, it readily converts to other compounds once it is formed. Therefore cooking, aging, crushing and otherwise processing garlic causes allicin to be converted into other compounds.
Although the consumption of raw garlic provides high allicin yields, it is also associated with a number of undesirable side effects, such as halitosis, body odor, and gastrointestinal disturbances. As a result, efforts have been made to develop a garlic supplement that provides the beneficial health effects of raw garlic without the undesirable side effects associated with its consumption.
Studies have shown, however, that many of the garlic supplements currently available release far less allicin under simulated gastrointestinal conditions. The difficulty in releasing allicin from garlic supplements is related to the fact that allicin is not present in uncrushed garlic or in garlic powder but is produced by the interaction between the allinase and aliin.
To prevent the decomposition of allinase by stomach acid, some manufacturers have enteric-coated garlic powders in order to bypass the stomach. However, simulated intestinal fluids have been shown to significantly reduce, or even completely destroy, allicin production even in enteric-coated garlic preparations. Moreover, allinase, the enzyme which catalyzes the conversion of alliin to allicin, has been shown to be irreversibly deactivated at pH 3 or below, an acidic environment typically found in the stomach.